<template>
</template>
<script>
  import Scroll from './scroll'
  export default {
    name: 'back-scroll',
    mixins: [Scroll],
    props: {
      flag: {
        type: Boolean,
        default: false
      }
    },
    methods: {
      onScroll() {
        const scroller = this.scroller
        const isWindow = scroller === window
        const height = Math.ceil(window.screen.height / 2);
        const scrollTop = isWindow ? scroller.scrollY : scroller.scrollTop
        // 监听页面已滑动的位置，当页面滑动半屏之后，显示“返回顶部”按钮
        if (scrollTop > height) {
          !this.flag && this.$store.commit('toggle', 1);
        }else{
          this.flag && this.$store.commit('toggle');
        }
      }
    }
  }
</script>
